Staging Environment: Content and features may be unstable or change without notice.
Advisory details: gitlab / pypi/nltk/CVE-2026-81725
Advisory ID gitlab/pypi/nltk/CVE-2026-81725
Aliases CVE-2026-81725
GHSA-8mpw-7fpc-4gqj
Summary NLTK: Pl196xCorpusReader has quadratic ReDoS on malformed TEI blocks `Pl196xCorpusReader` still parses whole TEI blocks with multiple lazy regexes over attacker-controlled text. A malformed file with many opening tags and no matching closing tags forces repeated rescans and produces quadratic CPU growth in public reader APIs.
Status Published
Exploitability 0.5
Weighted Severity 0.0
Risk
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (4)
CWE-400 Uncontrolled Resource Consumption
CWE-1333 Inefficient Regular Expression Complexity
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
cvssv3.1 https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-81725.yml
Reference id Reference type URL
https://github.com/nltk/nltk/commit/7808692d451b962711005d954859bb83aabcf8fa
https://github.com/nltk/nltk/releases/tag/v3.10.3
https://github.com/nltk/nltk/security/advisories/GHSA-8mpw-7fpc-4gqj
https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3752.yaml
https://www.vulncheck.com/advisories/nltk-before-3.10.3-regular-expression-denial-of-service-via-pl196xcorpusreader
CVE-2026-81725 https://nvd.nist.gov/vuln/detail/CVE-2026-81725
GHSA-8mpw-7fpc-4gqj https://github.com/advisories/GHSA-8mpw-7fpc-4gqj
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L Found at https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-81725.yml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.